Whitesell



Feb. 7, 1956 w rr s 2,733,556

NG AND POLISHINMND TH LIK Feb. 7, 1956 H. WHITESELL GRINDING ANDPOLISHING AND THE LIKE 3 Sheets-Sheet 2 Filed Nov. 5, 1953 Feb. 7, 1956H. WHITESELL 2,733,556

GRINDING AND POLISHING AND THE LIKE Filed Nov. 5, 1953 s Sheets-Sheet sUnited States Patent O 33556 amma AND POLISHING AND THE LIKE Ha r Whtest li t ng l ertl sfis Na alia 1953, r al 9 23 Cla ms- (Cl- 519-141)This invention relates to improvements in grinding and polishing, andthelike. Insuch operations the rate at which the material will beremoved from the work body depends largely on the length of the scratchproduced by the grinding element or elements engaging such work'body.That to say, for a given hardness and quality of material used in thegrinding tool the rate of removal of the material from the work bodywill depend largely on the lengths of the scratches produced in suchwork body by the grindingelement. When the tool is formed of very hardmaterial and is unyieldingly supported during the grindingopera'tion itis evident that, for operations in which the grinding tool rotates aboutan aiiis of rotation aurin'gwh'e grindingoperation, the scratches mustbe short, with correspondingly limited rate of stockremoval from theworlcbody. That this is true is evident since the noii-yieldability ofsuch grinding'elementfnecessarily limits the ajraof contact thereof withthe work body; If the ressure exerted between the grinding tool and theWork b'ody' hemmed so as toincrease the depth of the out? yvhichwill beproduced by the tool, to correspondingly increase the lengths of thescratches it will be seen that such attempted increase in the rate ofstock removal must necessarily result in production of curved groovelike depressions in the surface of the work body; the lengths oflthescrat ches being dependent solely on the depth of penetration of thetotating tool into the of the material of the work body itself.

It ha sbeen proposed in my co-pending application for Letters Patent ofthe Uhited States, Serial No. 377,521, filed August 3], 1953,12, formthecontact wheel which carries the abrasive grinding or polishing belt ofyieldable material so that during rotation o t-such wheel the lengths ofthe scratches prqdilceid by the belt at the location of the contactwheel may be correspondingly increased, thereby substantially increasingthe rate of removal of material from the'work body. It is now desired toobtain the benefits of long scratch effects by the use'of beltstravelling over contact wheels of substantial ly non-yieldable or hardmaterial, or byuse of abrasive wheels of either hard material orsemi-elastic material but which wheels are so constituted that theycomprise the abrasive elements themselves and produce the desired longscratch efiects. That is to say, it is a prime feature and object of thepresent invention to make possible vthe very substantial increase inscratch lengths and cutting rates which aredsired, but without'relyingon theluse of high contact pressures between the wheels and the workbodies needed to secure deep cuts, and, if desired, to secure thesebenefits and advantages while ,still making it possible to use hard,substantially non-elastic materials in the wheel itself? i In oneembodiment of the features of my present invention I provide a workwheel or contact wheel which is'provided with numerous segments of hardor substantially non-elastic material which comprise the working orpolishing or grinding surface *prdpeh andiwh-ich seg- 2,733,556 tenses.Eek: 7: 1 2

2. ments are backed by an elastic support against inward radialmovement; but such elastic support p'e'r'r'nits inward radial movemeutotsuch s'eg'm'erits "under pressure of'the work body; Under this ar gngemettuese nems'mgy be forced inwardly radially under the writ force pres;sure, thus enabling thto'ntacct'o be' mainta ed'be'tweeii each segmentand the su'rliac'e ofthe' we biid'y foifai substantial amount ofthe"angi1lar""moye'meiit' of "the grinding orpolishing"element?Accordingly, the lengths of the "scratches'produceilon the surface "of'the' "work body may be greatlyincreased'withoutcorrespondingly increasing the depth of-the' cutproducedinsuchwdrk body surface. With "such elastic"oryieldable'backingfor the segments each segment prqduces itsefiect'dtir a rotative angularm 'vement ofthewheeregrrespepqmg to the chord drawn between the point ofengagement of such segment'with the work bodysurfaceand the point ofdeparture from such e gagemen arid' thi's Jung scratch efiect isproduced notwithstanding the fact that the segment itself is made ofsubstantiallynon-e1a"s' ti or non-yieldable material:

According to another embodiment of the features of my presentinventio'ril may include an abrasivebelt oi surface" which travels oversuch '"seg'rhent s during" the wheel rotation, the actual'abrasiveifect'sbeingpro'duced by' such belt or'lik' surface; but 'in this"baseftobf the segments are formed of substantially non-elasticofnohyieldable material, but aresup'ported against the backing of yieldableorelastic material whib'h resists but p'erirlit's inward radial movementof each segment under thein ward radial force deileloped during thegrinding or polishing operation. Thus the lengths of the'scratch'es aregreatly increased with this beltarrangement,"sitiiilar in effect to theeffect produced"'when the segments them selves are in directcontact'with the surface "of the wtirk body.

When the segments themselves are in direct contact with the work' body"surface, they *are formed of abrasive, but hard and substantially'nonelastic material, orthe'y may be formed 6f e'lastic'or'yieliiablematerialbut'of abrasive qualities andchai'acteri'stics",bufe'a'ch" such abrasive segment orbody 'comp'rising a portion of'tlteworking surface of the wheel is able to yield-inward ra dially under thepressure'exert'ed againstifby thework body, thus ensurihga greatlyincreased lengtli'oFth'e scratch which it prodube's on the workbody'surface;

When the wheel segments are formed of abrasive material, they maycomprise 'any suitable abrasive material as a homogenous segmental body,or they may comprise suitable abrasive material in granular orlikeform'; bond'ed or .bound into the desired segmental"form"by suitablebinde'r. In -either the foimer or' the' lattei' ca'se, however, thesegments are coni'ehiently formed by 'a suitablemoulding process,eithei' withor'without 'th'e' ap plication of heat during the operation,and generally under heavy pressure a'l'nplied duringthe mouldingoperation. Examples of suitable bonding orbindiiig materials are such'inaterials as resinoid's,'rubbr, and other binder materials, an'dinsuch proportionsas'will ensure the desired abrasive "qualities in thesegments whe'n'fifiished. Examples of suitable abrasive materials whichmay be used in forming" such abra's'ive segments are'e'm. ery, aluminiumoxide, garnet, diamond,'silicon carbide, and other materials, ingranular" form, and bonddto gether as previously explained herein. i

When a segmented wheel is used in the grinding or polishing operation itis'seen that as each segment comes to the work surface of the work bodythere "will be pro duced a shocker blOw of the wheel segment against thework' body surface,'and when the wheel-isrotating'rapid ly and whenthere are numerous of the segments around the wheel, it is ev entlilies-the y qrk y subisi ed to a very rapid hammermill action inaddition to the grinding action itself. This double efiect will greatlyenhance the grinding action produced by the equipment. It is to benoted, however, that due to this hammerrm'll effect it is desirable touse material in the production of the segments which material is able totake the shocks and severe treatment produced by such very rapid impacteifectas just referred to. The resinoid and/or rubber binder materials,and other materials of like characteristics, are therefore very welladapted to the present uses. It'isa further feature and object of thepresent invention to provide a wheel construction such that theperipheral segmented portion of segments of desired or selectedmaterials and hardness may be of built up construction, readilyassembled or disassembled for substitution of segments 'of otherorreplacement materials; Thereby the usefulness of a given wheel structuremay be greatly widened and its useful life increased.

, Other objects and uses of the invention will appear from a detaileddescription of the same, which consists in the features of constructionand combinations of parts hereinafter described and claimed.

, In the drawings:

Figure 1 shows a cross-section through a typical wheel embodying thefeatures of my present invention, being a two-part section, the upperone-half section being taken on the line 1 -1 of Figure 2, looking inthe direction of the arrows, and the lower one-half section being takenon the line 1 -1 of Figure 2, looking in the direction of the arrows;

Figure 2 shows a partial development of the peripheral surface of thewheel shown in Figure 1, and shows a number (14) of the sets ofsegmental elements in their relationship to each other and to theintermediate rod supporting plates;

Figure 3 shows a partial longitudinal section of the wheel structureshown in Figures 1 and 2, being a section taken on the lines 33 ofFigures 1 and 2, looking in the directions of the arrows;

Figure 4 shows a semi-cross-section through a modified form of wheelembodying the features of my present invention, in which modificationuse is made of circular or ring shaped segmental elements; this figurebeing a twopart section, the left-hand half-section corresponding toFigure 1 and the right-hand half-section corresponding to Figure 1Figure 5 shows a semi-cross-section through another modified form ofwheel embodying the features of my present invention, in whichmodification use is made of segmental shaped blocks similar in form tothose shown in Figure 1; but in the present case said blocks are of sizeto come substantially together in each circular grouping, and the blocksare notched on their side faces to receive and accommodate the axiallyextending intermediate block supporting rods; and this figure shows atwo-part section, the left-hand half-section corresponding to Figure 1and the right-hand half-section corresponding to Figure 1 Figure 6 showsdiagrammatically the manner in which the length of the scratch varieswith the amount by which the segmental block is forced inwardly radiallyagainst the elastic resistance force of the backing block, assuming thatthe segmental blocks are formed of substantially nonelastic material;

Figure 7 shows diagrammatically an installation of grinding and/ orpolishing equipment including a contact wheel embodying the features ofthe present invention, and in which installation an abrasive materialcoated flexible material belt is used, running over the contact wheel,so that the abrasive action is produced by the surface coating of suchbelt, but under conditions dictated by the construction and functionaloperation of the contact wheel embodying the features of my presentinvention; and

Figure 8 shows diagrammatically an installation including a wheelembodying the features of my present invention, but in which wheelembodiment the segments are formed of abrasive material, so that thegrinding and/ or polishing function is performed by the elements of thewheel itself, no abrasive belt being included in the installation.

Referring first to Figures 1, 2 and 3, the wheel therein shown includesthe peripheral blocks 10 which are built into and supported in the wheelin such manner as to provide the peripheral, more or less segmentalcylindical surface 11. These blocks are so supported and built into thewheel that they may shift radially through a radial distance sufiicientto enable production of the functional effects presently to be set forthin fuller detail; and elastic resistance elements are provided radiallyinwardly of such blocks to resist such inward radial movement of theblocks. In the embodiment shown in Figures 1, 2 and 3, such elasticresistance elements comprise annular bodies of elastic material, 12,formed of rubber or other suitable material, and having the elasticcharacteristics needed to produce the desired resistance effects,according to the wheel design in question. The blocks 10 are supportedagainst outthrow under centrifugal or other forces by the axiallyextending rods 13 and 13 Conveniently the rods of the group 13 extendthrough radially elongated slots 14 formed in the blocks through whichthe rods 13* extend, and the rods of the group 13 extend throughradially elongated slots 14 formed in the blocks through which the rods13 extend, the blocks of the two groups breaking joints as willpresently appear in further detail. Conveniently, also the elasticannular bodies 12 are set onto cylindrical supports 15, which areaxially supported on or around the shaft 16, the details of whichconstruction will soon appear. However, I wish to emphasize thatalthough I have herein disclosed some of the details of the physicalstructure embodying the various elements thus far referred to, still Ido not intend to limit myself to such detailed structural features,except as I may limit myself in the claims to follow.

With the foregoing statement I shall describe the detailed structurefurther as follows:

Conveniently the blocks 10 are supported within the wheel periphery insuccessive groups, each group including a number of the blocks lying ina common plane normal to the axis of rotation. Preferably, also theblocks in successive groups break joints with each other, as shown inFigure 2. By this arrangement the effects of the joints betweensuccessive blocks during rotation are substantially eliminated, and moreuniform grinding or polishing action is produced.

The longitudinally extending rods 13 and 13 may be supported in anyconvenient manner. In the arrangements shown in Figures 1, 2 and 3 Ihave provided the plates 17, 17*, 17 etc., lying in planes normal to theaxis of rotation, and provided with peripheral through openings throughwhich the rods extend. As illustrated in Figure '2, the blocks are settogether in successive series, each series including the blocks of fiveof the groups, and the plates 17 17*, 17, etc. being located between thesuccessive series of five groups each. The plates are provided with theoutwardly extending cars 18 through which the rods extend. Convenientlya sleeve 19 is set over the shaft, and the plates 17 are strung ontothis sleeve. Spacers 20 are set on the sleeve between the centralportions of the successive plates, and, if desired said spacers may beconnected to the respective plates by welding, riveting or otherwise.These spacers are of size to fully extend between the successive plates;and the cylindrical supports 15 are set onto the spacers such supportsbeing of full dimension between the successive plates as indicated inFigure 3. Thus each of the elastic resistance elements 12 secures fullsupport for its inside cylindrical surface, and for the full distancebetween the successive plates.

A suitable end plate or block such as shown at 21 is ares-ass setagainst each end of the so-built up wheel, and*con veniently the rods 13aresecured into these endplates or blocks, as by threading, as shown inFigure 3; it being understood that there is an end plate or blockagainst the right-hand face of the Wheel, which, however, is not shownin Figure 3 due to lack of space on the drawing. Of course the wheel issuitably journalled for high speed rotation, and is driven in convenientmanner.

During construction of the wheel the parts may be so proportioned,including the radial dimension of the resistance elements, that somecompression is initially produced in said elements, so that the outwardradial forces developed against the blocks during running will includesuch pre-loading force, or, if desired, no such preloading may beproduced when no such compressive force or effect is required during theassembling of the wheel. It will also be understood that during runningof the wheel substantial centrifugal forces will be developed in theblocks, which forces will be additive to those due to the presence ofthe resistance elements, whether the latter be pre-loaded or not. Anyinward force developed against a block or blocks must therefore, besufficient to overcome the centrifugal force thus developed, as Well asany pre-loading force, before any inward displacement of the blocktowards the axis of rotation may be produced. Furthermore, assuming thatthe conditions of Hc-oks law obtain, it is evident that, in the case ofno pie-loading, the amount of inward displacement will be directlyproportional to the size. of such inward force; and that in the case ofany pre-loading, the curve showing variation of inward force withvamount of inward displacement will be raised by the amount of thepre-loading, plus the centrifugal force.

The permissible inward displacement of the blocks by ressure exertedagainst them, as by pressure of the work body against the periphery ofthe wheel, will be limited by the amount of force needed to eifect suchdisplacement, and the permitted radial movement, as determined by thelengths of the slots 14 in the blocks. The characteristics of design andmaterial of the elements 12 should be such that, under extreme pressuresenough compression of the said elements 12 may be produced to allowsubstantially full inward block displacement as limited by the lengthsof the slots 14. Of course, upon withdrawing such pressure against theblocks they will restore to their extreme outwardly limited positions,as

determined by the engagement of the slot ends with the rods 13.

Before proceeding further with a functional analysis of the grinding andpoiishing effects produced by wheels embodying my present improvements,I shall describe briefly the modified forms of wheel shown in Figures 4and 5. The wheels of these two modifications are substantially the samein outlines as the wheel already described; but the following principalpoints of difference between these Wheels and that of Figures 1, 2 and3, are

noted:

In the arrangement of Figure 4 the blocks comprise small wheels or disks22 which are strung on the rods in successive groups, with the disks ofsuccessive groups breaking joints as clearly indicated in Figure 4; andeach such disk is provided with a central opening of size larger thanthe rod which extends through such disk. Thus each disk may be displacedinwardly against the element 12, according to the principles alreadydiscussed. It is now noted that due to the fact that each disk is ofmuch smaller diameter than the diameter of the complete wheel it is seenthat even for extreme amounts of inward-radial movement of the disks,against the effects of centrifugal forces and the resistance of theelement 12 against which the disk or disks press, the contacting portionof each disk against the surface of a work body will almost always be apoint or at most a small discrete area, so that substantially a point.contact occurs between each disk and the wor body u ac thus n effectproducin true scratches. on the work body surface, and correspondinglines of material removal from the work body. It further noted that whenusing this. disk form of the blocks, each disk is more or less free. torotate gradually on its own rod support, thus continually presenting newpoint elements of engagement to the surface of the work body. Thus, too,each such disk may Wear more or less evenly around its periphery.However, the rate of disk rotation will generally be small due to thefrictional engagement of each disk with the elastic element 12 againstwhich it presses; and that frictional engagement will generally be largein amount. The coeflicient of friction of the metal of the disk againstthe material of the elastic body (generally some form of rubber) may andfrequently will be actually larger than the coefficient of friction ofthe disk against the metal surface of the work body being treated.

The arrangement shown in Figure 5 is similar to that shown in Figures 1,2 and 3; but in the case of Figure 5 each of the blocks 10 is providedwith the lateral face recesses 23 which may accommodate the proximaterods, thus permitting the blocks of each group to be set closertogether, center to center than is possible in the arrangement ofFigures 1, 2 and 3..

We may next explore more fully the functional effects produced duringthe grinding or polishing operation by devices embodying my presentimprovements. In this connection I here mention again the fact thatwheels embodying my present improvements maybe formed of material havingthe desired abrasive qualities in its own body, or or" neither abrasiveor non-abrasive material with a flexible belt running over the wheel,and having a surface provided with the abrasive quality. To the end ofsuch study, reference. may again be had to Figure. l. Therein I haveshown by the line 24 a surface line of a work body which is sustainedagainst the wheel periphery with force sufiicient to displace the blockinwardly some distance. It is seen that this line subtends a chordbetween the points 25 and 26, they length of which chord is dependent onthe amount of the inward radial displacement, and on the radius of thewheel periphery prior to the displacement (that is, the normal radius ofthe Wheel). Mathematical analysis will show that the length of the chordmay be expressed as follows I L=\/2zia,' where L equals the length ofthe half-chord and d equals the displacement, so. that the full chordlength equals double. the value indicated by said equation. Study ofthis equation will show that for small angles of embracement representedby such chord the length of the chord varies almost directly as theamount of displacement, and for all practical purposes this conditionmay be assumed as true. If it be assumed that the wheel is rotating inthe direction of the arrow in Figure 1, and that a section of the workbody is held against the wheel at the line 2526 (or against the flexiblebelt riding 'on the wheel), as rotation continues clockwise the block10* will be pressed inwardly, with increase of force needed to effectsuch inward radial movement due to the needed compression of the elasticmaterial body 12, until the center of such block has come to thelocation of such elemental area of the work body. At that instant theblock will be most fully displaced inwardly. Then, as the wheel movementcontinues the block will move out to larger and larger radii positions,with corresponding reduction of the required displacing force, untilfinally the point 25 comes to the location of the elemental area 26 ofthe work body. Then that particular block will have completed itsfunction for the wheel rotation in question, and other succeeding blockswill go through similar functional processes.

In Figure 6 I have repeated the foregoing functional analysis in orderto simplify an understanding of the process being investigated. Thelocations of several chords of successive values of displacement areshown for better understanding and. clarity of the analysis.

It is further noted that the abrasive force developed betweeneach blockand the surface of the work body undergoes a progressive increase up tothe center of the chord, and then progressively decreases to zero at theleaving end of the chord. Also, that when the elastic body 12 ispie-loaded the total pressure exerted at the beginning and terminatingends of the chord are the amount of such pre-loading, and that atintermediate chord locations the pressures are all increased by theamount of the pre-loading, plus the centrifugal force.

The analysis just above given for the form shown in Figures 1, 2 and 3is also valid as respects the forms shown in Figures 4 and 5, subject topossible modification in case of rotation of the disks of the form shownin Figure 4.

It is also now seen that as the successive blocks of a group come intoengagement with the work body surface there is necessarily produced ahammermill efiect. This, combined with the improved abrasive effectserves to ensure a greatly increased rate of stock removal from thesurface of the work body. In fact, the aggressiveness of the grinding orpolishing device is magnified several times as compared with previouslyknown and practised devices and operations.

It remains to consider the fact that these improvements may be used inconnection either with wheels in which the blocks themselves are formedof abrasive material, some of which materials have previously beensuggested by way of illustration, or in connection with grinding andpolishing devices of the flexible belt-abrasive surface type. In Figure7 I have shown, more or less schematically, an arrangement in which thebelt 27 travels over the wheel 28, of the type previously disclosedherein, and over the idler wheel 29. This latter wheel may be supportedin such manner that its axis 30 may be drawn under a spring forceproduced by the spring 31 in direction away from the contact wheel 28,to thus retain the belt tightly in contact with such contact wheel. Thesurface of the work body in contact with the contact wheel is shown bythe line 24, and the effects produced are closely similar to thoseproduced in the analysis of the form shown in Figures 1, 2 and 3. Aslight modification of effect might, however, be traced to the presenceof the belt whose flexibility would nevertheless exert an influence onthe extent of displacement of the blocks, and have other modifyinginfluences. If, however, the belts flexibility were suflicient to affectthe transmission of the displacing forces to the wheel blocks it isprobable that only slight modification of the functions would beproduced by the belt.

In the showing of Figure 8 it is assumed that the blocks are formed ofabrasive material, and that no belt is run over the contact wheelitself. Insofar as the functional operations of the blocks formed ofsuch abrasive material is concerned the analysis previously givenrespecting the showing in Figures 1, 2 and 3 would apply as respects thewheel of Figure 8. I have already mentioned by way of example variousabrasive materials which may be used in the formation of the blocks butI wish to emphasize the fact that it is desirable to use block materialswhich are of sufficient toughness to withstand the severe shocksincident to their functioning in the intended manner; or, alternatively,blocks of abrasive material may be used which shall include in theircomposition, materials of some elasticity so that, combined with theirstrength and toughness they will withstand the aforesaid shocks, etc.

The peripheral bodies may be of any degree of hardness or softness, orany degree of abrasiveness or nonabrasiveness desired, according to theeffect which it is desired to produce on the surface of the work body,whether a grinding effect, either fine or coarse, a polishing efiect,either fine of coarse, or a combined grinding and polishing effect.

- I claim:

1. An abrasion producing unit including a'wheel element, means tojournal said wheel element for rotation about an axis, said wheelelement including a plurality of axially extending body supporting rodslying substantially within a circular cylindrical surface coaxial withthe axis of Wheel rotation, and including means to support said rods insaid cylindrical surface, a plurality of bodies strung on each of saidrods at regularly spaced axial locations, each body being provided witha through opening to receive the corresponding supporting rod and ofsize greater than such rod measured in direction radially of the wheelto permit movement of such body on such rod in radial direction withrespect to the wheel and to limit outward radial movement of such body,elastic means in the wheel urging said bodies outwardly radially withrespect to the axis of wheel rotation, the supporting rods and thethrough openings in the bodies being constituted to limit the outwardradial movements of the bodies at locations with those portions of theirsurfaces which are at greatest radial distance from the axis of wheelrotation lying substantially within the surface of a cylinder which isco-axial with the axis of wheel rotation, and abrasive surface materiallying substantially at said greatest wheel radial distance portion ofeach body and travelling angularly with such body.

2. Means as defined in claim 1, wherein the abrasive surface materialwhich lies substantially at the peripheral arcuate surface of each bodycomprises a portion of such body.

3. Means as defined in claim 2, wherein each of the bodies is composedof abrasive material.

4. Means as defined in claim 1, wherein the bodies are formed ofmaterial which is substantially non-elastic.

5. Means as defined in claim 1, wherein the bodies are formed ofmaterial which is elastic.

6. Means as defined in claim 1, wherein each of the bodies comprisessubstantially non-elastic abrasive material.

7. Means as defined in claim 1, wherein each of the bodies compriseselastic abrasive material.

8. Means as defined in claim 1, wherein the abrasive surface materialwhich lies substantially at the greatest radial distance portion of eachbody comprises abrasive material surface of a belt travelling on the rodsupported bodies.

9. Means as defined in claim 1, wherein the rod supported bodies havearcuate peripheral surfaces comprising substantially portions of acylindrical surface which is co-axial with the axis of wheel rotationfor all radial positions of such bodies.

10. Means as defined in claim 1, wherein the rod supported bodiescomprise annular disks strung on the rods and journalled on the rods forrotation of said disks on the rods with their greatest wheel radialdistance portions lying within the peripheral cylindrical portion of thewheel element.

11. An abrasion producing unit comprising a wheel element, means tojournal said wheel element for rotation about an axis, a plurality ofrods, means to support said rods within the wheel element and lyingsubstantially within a cylindrical surface co-axial with the axis ofrotation, a plurality of bodies having arcuate peripheral surfaces,lost-motion means Eo support each of said bodies on a rod, the lostmotion means which supports each body on a rod including a throughopening in such body of size greater than the rod in direction extendingradially of the wheel, elastic means urging the bodies outwardlyradially with respect to the axis of wheel rotation, said lost-motionsupporting means being constituted to limit the outward radial movementof the bodies under the urging of the elastic means, and abrasivesurface material lying substantially at the peripheral arcuate surfaceof each body and travelling with such body.

12. Means as defined in claim 11, wherein the abrasive body.

13. .Means as defined in claim 12, wherein each of the bodies comprisesabrasive material.

14. Means asdefined in claim 11, wherein the abrasive surface materialwhich lies substantially at the peripheral arcuate surface of each bodycomprises abrasive material surface of a belt travelling on the arcuatebodies.

15. An abrasion producing unit comprising a wheel element, means tojournal said wheel element for rotation about an axis, an even number ofrods, means to support said rods within the wheel element and lyingparallel to the axis of wheel rotation and within a cylindrical surfaceco-axial with the axis of wheel'rotatio-n and at locations substantiallyequidistant around the wheel element, the rods comprising twosets ofrods, each set including alternate rods measured around the wheelelement and the rods of each set alternating with the rods of the otherset, a series of groups'of arcuate bodies having arcuate peripheralsurfaces, each such group including one-half as many bodies as thenumber of rods and the bodies of each group lying within a planeextending normal to the axis of wheel rotation, and lost motion means tosupport each body on a rod and including a through opening in such bodyof size greater than the rod in direction extending radially of theWheel element, the bodies of each group being located on the rods of aset of rods and the bodies of successive groups being located on therods of the two sets in alternation, whereby the bodies of each groupbreak joints with the bodies of the adjacent groups of bodies, andabrasive surface material lying substantially atthe peripheral arcuatesurface of each body and travelling with such body.

16. A unit as defined in claim 15, together with elastic means urgingeach of the bodies radially outwardly on its rod of support.

17. A unit as defined in claim 16, wherein said elastic means comprisesa cylindrical body of elastic material having its outer cylindricalsurface in engagement with the radially inward portions of all of thebodies, and means to support said body of elastic material within thewheel element and coaxial with the axis of wheel rotation.

18. Means as defined in claim 16, wherein said elastic means normallyretains each of the bodies in its most outwardly moved position radiallyof the wheel element.

19. Means as defined in claim 16, wherein each of the bodies is ofsegmental contour with its convex surface lying in the outer perimeterof the wheel element and is of angular embracement extending between twoof the rods of the set other than that set including the rod on whichsuch body is located.

20. Means as defined in claim 16, wherein each of the bodies comprises adisk of open center annulus form, and wherein the rod on which such bodyis located extends through the open center of such disk.

21. Means as defined in claim 20, wherein the open center of each diskis circular and of size greater than the diameter of the rod on whichsuch disk is located.

22.v Means as defined in claim 15, wherein the means to support the rodswithin the wheel element comprises a series of disks lying in planesnormal to the axis of wheel rotation and spaced apart axially of thewheel element distances which are multiples of the dimensions of thebodies in direction parallel to the axis of rotation, and wherein therods are supportingly connected to the peripheral portions of suchdisks.

23. Means as defined in claim 22, together with spacer elements locatedbetween the proximate faces of such disks, and wherein the dimensions ofsuch spacer elements in direction parallel to the axis of rotation aresubstantially equal to the additive sum of the dimensions of the bodieslocated between the disks spaced by such spacer elements.

References Cited in the file of this patent UNITED STATES PATENTS267,132 Belding Nov. 7, 1882 401,215 Ross Apr. 9, 1889 675,915 WoodsJune 11, 1901 1,393,625 Hobbs Oct. 11, 1921 1,484,353 Kidwell Feb. 19,1924 2,099,207 Hill et al Nov. 16, 1937 2,410,536 Vonnegut Nov. 5, 19462,466,030 Landau Apr. 5, 1949 2,527,554 Kimball Oct. 31, 1950 2,581,270McVey- Jan. 1, 1952

